1. Field of the Invention
The invention concerns a method and transmission arrangement for changing gears in a transmission with a hydrostatic transmission and a manual gearbox connected downstream from it.
2. Discussion of the Prior Art
To increase the possible range of gear ratios of a hydrostatic transmission, connecting a manual gearbox downstream from the hydrostatic transmission is known. Such a transmission arrangement is known from DE 42 23 846 A1. To be able to change gear in the downstream manual gearbox, the hydraulic motor of the hydrostatic transmission is set to a pivoting angle of approximately 0. In this way the output torque of the hydrostatic transmission is reduced so much that almost load-free changing of the engaged gears in the downstream manual gearbox is possible. The required change of rotational speed of the output shaft of the hydrostatic motor is made by the synchroniser rings of the downstream manual gearbox. In this way, after an engaged gear is disengaged by the application of the synchroniser ring of the gear to be engaged, the hydraulic motor, which can be rotated practically without moment, is brought to the rotational speed which corresponds to the gear to be engaged.
It has been shown to be disadvantageous that because of the large rotational speed jumps, the wear on the synchroniser rings is considerable. In particular, because of the inert mass of the hydraulic motor and the existing drag torque of the hydraulic motor, the synchroniser is considerably stressed. When the synchroniser rings are applied while the next gear is being engaged, it is also disadvantageous that the suddenly occurring additional moment of the hydraulic motor ensures a considerable shifting jolt.